/Engine/Source/Runtime/Engine/Classes/GameFramework/Character.h
Set a pending launch velocity on the Character. This velocity will be processed on the next CharacterMovementComponent tick, and will set it to the "falling" state. Triggers the OnLaunched event.  LaunchVelocity is the velocity to impart to the Character  bXYOverride if true replace the XY part of the Character's velocity instead of adding to it.  bZOverride if true replace the Z component of the Character's velocity instead of adding to it.
virtual void LaunchCharacter ( FVector LaunchVelocity, bool bXYOverride, bool bZOverride )